Gallucci, 42, pleaded guilty Friday to a single count of conspiracy to commit bribery in U.S. District Court.
Sentencing was set for April 13.
The Republican ran for Cuyahoga County auditor in 2006 against a person identified in federal documents only as a public official.
Frank Russo, the Democrat who won re-election as auditor, has not been charged and has denied wrongdoing.
Gallucci landed a $67,849 per year job with the auditor's office after dropping out of the campaign.
Russo could not be reached for comment.
A message was left at his office Friday after regular business hours.
The Associated Press